var element_array = ['content_item_1', 'content_item_2', 'content_item_3', 'content_item_4', 'content_item_5', 'content_item_6', 'content_item_7', 'content_item_8', 'content_item_9', 'content_item_10', 'content_item_11'];
var current_index = 0;

function string_to_float(text){
  return parseFloat(text || '0');
}

function scrollPrev(){
  if (current_index > 0){
    moving = string_to_float($(element_array[current_index]).getStyle("width"));
    new Effect.MoveBy($(element_array[current_index]).parentNode, 0, moving, {duration: 0.7});
    --current_index;
  }
  return false;
}

function scrollNext(){
  if (current_index < element_array.length - 1){
    moving = -string_to_float($(element_array[current_index]).getStyle("width"));
    new Effect.MoveBy($(element_array[current_index]).parentNode, 0, moving, {duration: 0.7});
    current_index++;
  }
  return false;
}

function prepareScroll(){
  var content_count = (document.getElementsByClassName ? document.getElementsByClassName('content_item').length : 3);

  element_array = new Array(content_count);
  // content_id = 'content_item_1';
  content_id = 'content_item_';
  content_count.times( function(i){
    element_array[i] = content_id + (i + 1);
    // content_id = content_id.succ();
  });

  $("navigation_prev").onclick = scrollPrev;
  $("navigation_next").onclick = scrollNext;
  $("navigation_next_5f").onclick = scrollNext;
  $("navigation_next_2").onclick = scrollNext;
}

window.onload = prepareScroll;